Detecting Changes in Population Trends for Cook Inlet Beluga Whales Using Alternative Schedules for Aerial Surveys

Measuring population trends, and detecting a change in the trend, of Cook Inlet beluga whales (Delphinapterus leucas), has a specific role in the co-management agreement that determines harvest levels. It also has a more general application in the management of the population. An annual aerial survey schedule has provided abundance estimates used to determine growth trends for this population. Under the harvest co-management agreement, the measured trend over a 10-year period is used to classify the population into one of three growth categories: high, intermediate, or low. The growth category, along with the average abundance over the last 5-year period, is used to determine the number of takes allowed over the next 5-year hunting period. For a more general application, we would like to be able to detect a change in the growth rate of the population that results from a change in the underlying life history parameters and identify the year that the change occurred. Life history parameters include birth interval and rates of survival.